Biological materials frequently contain a high content of proteins in addition to a low content of further components. When the protein content is high, the components can be qualitatively and analytically detected only with difficulty, for example when checking the medicament level when administering immunosuppressive medicaments or the metabolites thereof from blood, plasma or serum samples.
Liquid biological materials such as plasma samples (and other clinically relevant fluids) are typically tested for the quantitative content of biomarkers (low-molecular-weight, organic compounds) by means of ELISA assays (linked immunosorbent assay) in order to record a disease progression or to diagnose a disease in the first place. In recent years, LC-MS (or LC-MS/MS) has started to establish itself as an alternative to ELISA assays. Typically, for this purpose, the plasma sample is removed from plasma proteins by means of precipitation and subsequent centrifugation and, subsequently, the low-molecular-weight compounds are separated in a reversed-phase LC, quantified (area of the LC graph) and the molar mass analyzed by mass spectrometry (MS).
In this connection, the protein removal is usually carried out manually, since centrifugation steps (or alternatives such as suction through a membrane by means of vacuum or pressure) are difficult to automate.
It is known that, depending on the origin of the sample and the analytical question, the qualitative and quantitative proportion of a trace component from a biological sample can be carried out on different instrument platforms and for different end-applications, such as clinical checks, doping tests, forensic and toxicological reports and tests. Regardless of the technological development for the readout of the experimental data, such as, for example, the technological development in mass spectrometry, a pretreatment of the analytical sample for the purpose of reducing complexity is still necessary.
Fundamentally, the analytical process is divided into five steps from the collection of samples up to the final result:
1) collection of samples,
2) preparation of samples,
3) fractionation of samples,
4) detection of analytes and
5) evaluation of data.
In most cases, a substantial amount of time is expended on steps 1) and 2).